Gas-liquid contacting apparatus



April 28, 1959 -J. MAILLE .GAS-LIQUJ ID CONTACTING APPARATUS 4 Sheets-Sheet 1 Filed March 10, 1955 21/6422 JEAN Mm:

7 April 1959 J. MAILLE 2,834,236

GAS-LIQUID CONTACTING APPARATUS Filed March 10, 1955 4 Sheets-Sheet 2 April 28, 1959 J. MAlLLE GAS-LIQUID CONTACTING APPARATUS 4 Sheets-Sheet 3 Filed March 10, 1955 April 28, 1959 J. 'MAILLE 2,884,236

GAS-LIQUID CONTACTING APPARATUS Filed March 10, 1955 4 Sheets-Sheet 4 GAS-LIQUID CGN TACTIN G APPARATUS Jean Maille, Montreal, Quebec, Canada, assignor to LAir Liquids, Societe Anonyme pour lEtude et lExploitation des Procedes Georges Claude, Paris, France Application March 10, 1955, Serial No. 493,448 Claims priority, application France March 11, 1954 12 Claims. c1. zap-114 This invention relates to two-phase contacting devices for gas and liquid and more specifically to the design of trays for use in this field. v

Recent developments in the field are outlined in A Technical Manual reprinted from the Oil and Gas Journal (1954) entitled Fractionation and Absorption for the Process Man and in an article in the Industrial Chemist 'for October 1953 entitled Recent Developments in Two-Phase Contacting Devices.

This invention is directed to the type of fractionating device which employs a tray of the type perforated with openings of a size such that when the tray is in operation they permit gas to ascend but prevent the liquid from des'cending. The type of tray is known generally as a perforated tray. The liquid flows across the tray from an onflow zone to an oil-flow zone while the gas passes up through the openings and through the layer of liquid on the tray. This type of flow across the tray is generally known as cross-flow as distinct from flow through the tray which takes place in a sieve" type tray.

Perforated trays employing cross-flow are simple in construction and have a high efficiency. Buttheir efficiency can only be maintained Within relatively narrow limits of through-put.

The applicant's development The present invention is designed to permit wide variations in through-put in an apparatus employing a column including a number of spaced apart trays one above the other in which each tray is adapted to support a liquid layer and to allow permeation of the liquid layer by the rising gas. In accordance with the invention rising gas is channeled into a multitude of small spaced apart courses which are brought into contact with the liquid layer at different depths of levels in the liquid layer and positively bafiied except at the courses. tacting the liquid layer at the least depth form streams, or jets of bubbles which penetrate the liquid even though the gas pressure is low. The gas in the difierent courses being at substantially the same pressure, the courses contacting the liquid at the greatest depth penetrate the liquid only when the gas pressure is at the highest, whereas the courses reaching the liquid at an intermediate level are effective at both intermediate and high gas pressures. This is because of the differential in the head of liquid above the respective courses. The greater head of liquid above the courses encountering the liquid layer at the deeper levels olfers greater resistance than the lesser head at the shallower levels. At least some of the intermediate courses are directed downstream to exert a thrust on the liquid when their jets are active. Preferably the up ward flow of the gas stream is bafiled directly beneath the lower and intermediate courses so as to cause the gas to change direction before being channeled into the courses. This is to disentrain liquid from the gas. In accordance with the invention, the courses are so directed that the resultant force including that of gravity and the The courses conn d aws Far "ice resultant thrust of the gas on the liquid layer is downstream.

This apparatus of the invention employs a specially designed tray'. This tray has in common with trays of the prior art an elongated liquid retention surface across which the liquid will be made to flow (in cross-flow as opposed to sieve flow) and gas holes through which the gas passes under certain operating conditions into and through the liquid stream. The tray includes receiving means for receiving liquid from above and downcomer means for passing the liquid to below, and the necessary In ac: cordance with the present invention the tray has a plate-' like supporting member providing the liquid retaining This surface is bumpy, preferably undulating.

parts to retain the tray in position in a column.

surface. v This bumpy surface is made up of a series of hills and third group of gas holes.

stream slope or is imperforate. nel the gas into courses and direct it against the stream of liquid passing over the surface of the supporting mem ber. Depending on the gas pressure the thrust of the gas in the courses will be suflicient or not to overcome the head of liquid above it and to pass through the hole and into and through the liquid as a stream of bubbles. The gas will tend to seek the holes above which the head is least, so that at low gas pressure the gas will only pass through the holes at the summit of the hill. mediate gas pressures the gas will pass through the open ings in the slope of the hill as well. At high gas pressure the gas will pass through all the holes.

of trays, one spaced above the other. The t'rays meet the wall of the tower and form a seal against the rising gas except through the gas holes in the liquid-supporting" surface.

It is evident that the first and second group of holes are neutral, i.e., they do not exert any downstream or d plus 11 is greater than u d is the area of the downstream holes (01' courses), n is the area of the neutral holes (or courses) and u is the area of the upstream holes (or courses). The valu'e of u may be zero or greater and d should not be less than half of u.

In accordance with normal gas-liquid contacting practice the total area of the gas holes in the tray will be from about 7% to about 15% of the total liquid contacting area of the tray including the area of the holes. This holds for any size of tray. In typical trays the individual openings will range from about 1 mm. to about 3 mm. in diameter but this may vary depending on the number of holes and their distribution. The specific size of the:

holes for any particular tray within this range will depend on the K value of liquid-gas. The diameters given are,

of course, for circular holes which are the most practical.

At inter A fractionating: or washlng tower 1s, as 1s usual, provided with a number In accordance with the invention, there-- 3 If the holes should be other than circular the areas should be within about the same range.

Preferably gutter-members are provided beneath the second group of gas holes and at least a part of the third group of gas holes. These gutter members serve the dual purposes of deflecting the gas and causing it to change direction before it is channelled into the gas holes and of catching liquid which may weep down through the gas holes. Deflection of the rising gas causes disentrainment of liquid into the gutters. Retention of the liquid provides a stock of liquid for starting up after a shut-down.

One preferred way of making the plates is by forming them from a series of overlapping identical corrugated strips, each strip being provided with a main undulation and adjoining trough and upsweep portions beside each trough. The strips are overlapped in such a way that they form the plates.

An alternative form of tray is formed in the following manner.

This tray is similar in construction and in function in respect of the actual liquid supporting surface. However this surface instead of having hills and valleys running across the tray has these hills and valleys running concentrically about the tray from a liquid receiving portion at the periphery to a downcomer near the centre of the tray. The liquid supporting surface is preferably made up of a number of annular corrugated rings instead of the strips of the previously described form of the device. The outer ring is provided with means for engaging the wall of the column. The inner ring is provided with means for engaging a receiving vessel. The liquid runs from the periphery of the tray towards the centre, i.e., across the corrugations. Liquid conveying members are provided running from the receiving vessel at the centre to the periphery so as to deliver liquid from this vessel to the tray below.

The invention has been generally defined and now it will be referred to in more detail by reference to the accompanying drawings which show preferred embodiments of the apparatus and in which:

Figure l is a fragmentary perspective view of a fractionating tower equipped with trays in accordance with the invention.

Figure 2 is a vertical cross-section showing the relationship of several successive trays in the tower shown in Figure 1.

Figure 3 is a fragmentary vertical cross-section taken through one of the trays of Figure I intended to show particularly the movement of the liquid and gas.

. Figure 4 is a horizontal cross-section through the tower showing one of the trays in plan view.

Figure 5 is a fragmentary view of the plate portion of one of the trays.

Figure 6 is a fragmentary plan view of the plate shown in Figure 5 illustrating more accurately the disposition of the gas holes.

Figure 7 is a fragmentary plan view showing a part of one of the strips from which the plates of Figures 5 and 6 is made, the strip being shown flat before corrugating.

Figure 8 is a horizontal cross-section through the tower showing a tray of an alternative form, e.g., an annular form.

Figure 9 is a vertical cross-section along the line 9--9 of Figure 8.

Figure 10 is a vertical cross-section along the line 10-10 of Figure 8.

Figure 11 is a large fragmentary vertical cross-section through the plate portion of the tray of Figure 8 taken along the line 9-9.

Figure 12 is a graph illustrating the efliciency of a tray according to the present invention as compared with that of prior art trays.

More specific reference will now be made to the drawings.

A steel fractionating column A is provided with a number of trays B, B B which are held in position in the column as will be described. The respective trays are similarly lettered but successive trays identified by the addition of the subscripts 1, 2, etc. The parts likewise of the trays are similarly numbered but those of successive trays carry a, b, etc.

Each tray is circular in outline and designed to fit within the column. Each tray is made up of a receiving plat form 15, 15a, 15b, etc., followed by a liquid supporting plate P, P P etc., and a downcomer 19, 19a, etc. Each tray is mounted on the wall of the column by being fixed to a metal L member 21, 21a, etc. This is suitably fixed to the column for example by soft soldering or in any other manner. Spacer channels 30, 33, 34 and 35 intervene respective trays. The spacer channels are spaced apart by tie rods 25 bolted as at 27. The spacer channels are provided with escapement openings 29 to allow liquid to circulate laterally and to find a common level over the entire tray.

Tray construction The construction of the individual trays is as folship on top of the space channel 30 as best shown in Figures 3, 5 and 6. Each strip is formed with substantially the undulating cross-section shown in Figures 3 and 5.

Each strip has a wave 33 which is flanked by an upstream wall 35 and a downstream wall 37. The down stream wall merges into a trough portion 39, and con-.

tinues into an upsweep portion 41. The upstream wall extends into a trough 43 and thence to an upsweep portion 45.

The adjacent strips are arranged in overlapping relationship so that the upsweep part 45, the trough 43 and the upstream wall 39 of one strip underlie respectively the downstream wall 37, the trough 39 and the downstream wall 41 of the preceding strip. Thus, the portion 35 of the underlying strip is in contact with the portion 41 of the overlying strip leaving the portions 43 and 45 of the underlying strip spaced from the overlapping portion 37 of the overlying strip. The strips, therefore, make up a plate the upper surface of which provides the liquid sup porting surface of the tray and the underlying projecting portions, gutter members.

The ends of the strips are held in position by the flanges of the members 21, 2111, etc. Actually, the intermediate portions of the strips are not connected but merely in contact with one another.

For the purpose of allowing gas to permeate the sheet and to reach the liquid layer on top of it the following structure is provided. A first group, in this case, a single row of gas holes 61 is provided running parallel to the waves at or adjacent the crest of each wave. A second group, in this case, a single row of gas holes 63 is provided in the trough between adjacent waves. In the preferred form shown a third group of gas holes, in this case, made up of three rows65, 67 and 69 is provided in the downstream wall of each wave.

In accordance with the normal practice in gas liquid contacting apparatus using cross-flow the total area of the gas holes in the tray is between about 7% and about 1 15% of the total liquid contacting area of the tray. In the preferred form shown the total area of the holes presents about 15% of the total liquid contacting area of the plate.

It should be understood, however, that these dimensions are not limiting and that they can be varied over a v reasonably wide range having regard to the description elsewhere in this specification.

agsgaae The pre e e o m .of h vshqwn. is made t halves held together centrally by aspecial' joint; This joint includes the pair of channelmembers 33 and 34 placed back to back as shown. The plate B is made in two portions Ba and Bb. The strips S are prefabricated in two halves, each terminating at the central joint.

A certain amount of latitude for expansion is provided at the joint. This is only one way of making the tray and the strips can be continuous right across the tray, if desired. Or, the tray can be made of superposed corrugated plates suitably provided with openings and suitably placed with respect to each other. Other arrangements may also be used.

Operation The column is operated generally speaking in the same manner as any reflux column. For example, if liquid oxygen is being purified liquid oxygen flows from the top of the column to the bottom and gaseous nitrogen upward through the column. The same principle applies to the contacting of the other liquids with corresponding gases.

The effect of the present process is as follows. When the tray functions at low through-puts of gas, the pressure of the gas is relatively low and only the first group' of openings 61 are active.

' When the pressure of the gas is sufficient that it forces its way through the intermediate or third group holes as well the gas exerts a thrust on the liquid in a downstream direction.

The horizontal thrusts of the oblique jets of gas andthe vertical thrusts combine to give a good agitation without accelerating the liquid. The liquid flows then principally because of the difierence in its level between the on-- put and the out-put zones However, when the out-put of the tower and the pressure of the gas rises, the circulation of the liquid must become faster. The invention provides thatthis is accomplished automatically by the hori-' zontal thrust of the supplementary gas leaving by. the holes 61.

When the thrust of the gas rises further, the propulsion by the jets of gas going through the third group of holes could become such that the liquid would be entrained ata speed greater than the most favourable speed. The pressure of the gas then renders active the holes at'the bottom of the undulations. At this point, the combined action of the vertical jets of gas leaving the valley holes gives to the liquid in each undulation a turbulent move-w ment in a vertical plane. This slows the horizontal circulation of the liquid.

The passage of gas through the column can be said to' follow the following pattern. It rises as a stream between the trays. iarts of this stream rise more or less directly from the surface of the liquid on one tray to the underside of the tray above. Other parts of this stream are diverted by gutter or baffle members, i.e., the parts 43 and- 45 of the strips before gaining access to the underside of the liquid carrying portion of the plate. Gas reaching the tray is channelled into or against the gas holes in the tray or baffled by the imperforate portions. The gas channelled into or against the gas holes has been referred to in a process sense as being in courses as distinct from the gas which finds itself for the time being baffied. The gas in these courses is either in the form of a stream flowing into the liquid, when its pressure is high enough to I overcome the head of the liquid above the gas holes,

6*- is a l a t in. pos tio o. pass hro h th op ning. w en the gas pressure is sufliciently hi'ghi The particular arrangement of the gas holes thus permits:

(1) The diminution of the hydraulic gradient by th utilization of a part of the kinetic energy of the gas and preventing the drowning of the column, when the latter functions beyond its theoretical capacity.

(2) Maintaining a desirable turbulence in the liquid no matter what the gas pressure resulting in good tray efficiency (diagram 1).

(3) Lowering the influence of the through-put on the loss of liquid charged from the tray.

(4)The elimination of accumulations of liquid on the tray when the ratio of reflux rises or when the tray finds itself situated at the level of the feeding of liquid.

If the functioning of the column is held up by interruption of the circulation of gas and liquid the liquid is no longer held on the tray by the pressure of the gas. The tray will then weep and gas will run partly through the orifices. But' part of the liquid remains in the undulations which have no openings, these undulations thus forming gutters-below the perforated parts 2 of the adjacent upstream, elements. The column will then operateas soon as the gas flow is re-established.

The form and arrangement of the gutters which maskv certain of the holes of each undulation become the linear ascending passage of the gas. sented on Figure 3 pass along each gutter and give ofi liquid particles with which they are charged after pas sage through the layer of liquid. So the amount of liquid is not altered by the entrainments (diagram 3).

Figures 8 through ll show an alternative form of trayi according to the invention. In this particular tray, the

circulation of liquid is from the periphery towards the centre. Each tray is made up as in the trays described in the previous figures, of parts enabling it to be attached to the column A The general construction of the tray' is in many ways similar to that described in connection 7 with the tray in which the flow is cross-wise rather than from the periphery towards'the centre.

The liquid supporting surface or plate D is made up of a number of annular rings R, each ring with the exception of the outer and inner rings is provided with a central hill portion 133, a downstream slope 137, a trough portion 139, an upsweep portion 141, an upstream slope 135, a trough portion 143, and an upsweep portion. 146.. The outer or peripheral ring R1 is provided with an up-- sweep portion 145a. which is somewhat longer than the normal upsweep portion and forms a rim which engages the wall of the tower A In the inner member R the slope 137A continues in stead of terminating in a trough and has an end portion R2 which is connected'to thetop edge of a bowl 115 which constitutes a receiving vessel for-liquid. The mern'fl L ber 115 has a downc'omer portion 11.6 for receiving the liquid from the plate D.

Going through the downcomer 116 and leading fromthe vessel is a curved pipe 190. One end of this pipe enters the vessel 115 where it ends in a month 118 which is more or less horizontal but oblique to the axis of the tube.

orin position as a potential'streaim ready to how i-m---,

The free opposite end of the tube 190 is preferably cut at 120 also in a section oblique to the axis of the tube. Thanks to' the oblique mouth of the tube entering into the vessel 115, the tube offers to the passage of liquid a greater surface than the cross-section of the tube. This diminishes the loss of the charge due to a change of direc tion of the liquid. By giving both ends of the tube a section having a same angle with the axis, it is possible that all the tubes can be obtained from tubes arranged in a "helix and cut. identically with minimum labor and with noloss of material. The tube preferably has at its highest portion, an opening 126 permitting equilibrium 75 in pressure between the tube and the gaseous atmosphere The gas streams repre- '2' underneath the tray, and avoiding siphoning from the vessel 115, in the case when the tube becomes full of liquid.

The portion of this tray as will be evident is very similar to the tray shown in Figures 1 to 7.

As will be understood by anybody skilled in the art usual materials can be used for making the parts of the trays in accordance with the invention. Copper has been found to be a suitable material for the strips S but other metals can be used.

Example The following are the characteristics of a typical low pressure column in an air separation plant equipped in accordance with the invention.

Capacity-1500 standard cubic meters per hour at 15 C.

and at a pressure of 760 millimeters of mercury. Tray design-based on 15,000 standard cubic meters per hour called for 100% capacity.

Diameter, 63 inches (1,600 millimeters) Area=2.0100 square meters Spacing of trays, 100 millimeters Square tray area (1.0 69 x 1.060)+2 sectors of 1.127 square meters+.243 square meter=1.366 square meters. Open area for vapor=.l700+.0117=.1817 square meter. Working area, 1.366 square meters Ratio between open area and working area=13.6% average. Vapor load per 1,000 moles of feed air=745 moles Working pressure=1.3 atmospheres (absolute) Working temperature =188 C. Actual fiow of vapor=.97 cubic meter per second for 100 cubic meters of feed. Actual speed of vapor flow into column=0.625 meter per second. Actual speed of vapor flow into the courses=4 meters per second. Pressure drop=1.2 inches of water per tray Purity obtained with 55 trays at vaporizer outlet 99.5% oxygen, at top of low pressure column=98.9% nitrogen.

Graph Figure 12 demonstrates the stage etficiency of the applicants type of tray as compared with certain other types of perforated trays. The eificiency was calculated in each case according to the formula Where ES=stage efficiency X =composition of vapor entering X =composition of vapor leaving X =ideal equilibrium between liquid and gas.

S=sieve tray.

T=aunular tray of the bubble cap type.

U=a louvre plate type of tray.

V=the annular type of tray of the present invention. W=the angular type of tray of the present invention.

Characteristic dimensions for a liquid carrying sheet used in a tray such as that of the example are as follows. The reference numerals are those in the drawings.

-Gas holes 61, 65, 67 and 63 circular 2.6 millimeters in diameter (area 5.34 square millimeters).

- Gas holes 69 circular 2.1 millimeters in diameter (area 3.46 square millimeters).

The horizontal pitch distance from the top 33 of one bill to the top 33 of the next 1 and 7 inches.

The horizontal distance between the bottom of the trough 43 and the adjacent top 33 in the upstream direction being 1 and inches.

The horizontal width of the corrugated sheet from upsweep to upsweep 2 and inches.

The vertical distance between the top of the hill 33 and the trough 43 being inch.

The vertical distance between the downstream upsweep 41 and the trough 37 being inch.

The horizontal distance between the top 33 and the downhill trough 37 being inch. 7

The horizontal distance between the trough 37 and the leading edge of the upsweep portion inch.

The vertical distance between the trough 43 and the leading edge of the upsweep 41 being W inch.

Gas holes As indicated earlier in the specification, the area of the gas holes should be according to the formula d plus n is greater than u where d is the area of the downstream holes (or courses), n is the area of the neutral holes (or courses) and u is the area of the upstream holes (or courses). The value of u may be zero or greater and d should not be less than half of a.

In a washing column, for example, d plus It may not be considerably greater than u. For instance, presuming that the holes are all of the same area and there are the same number of holes in each group (that is, each group has the same total area) a satisfactory arrangement is two groups of neutral holes at the top of the hills and the bottom of the valleys respectively, one group of downstream holes on the downstream slope of the hills, and $3: group of upstream holes on the upstream slope of the A typical arrangement for a fractionating column includes one group of neutral holes in the top of the hills, one group of neutral holes in the valleys, one group of up- Zil'ffim .holes and two or three groups of downstream The term resulting area means not only the direction of flow but that there are more openings in the direction of flow than elsewhere.

I claim:

1. A tray for gas-liquid contact, of the type having an elongated liquid retention surface across which liquid is made to flow substantially horizontally in a layer in contact with the gas rising through holes in said surface, a perforated plate-like member providing said surface and having a plurality of corrugations extending crosswise to the flow direction of the liquid, the corrugations providmg a number of undulations having hills and intervening valleys, the summit of each hill being provided with a first group of gas holes, each valley being provided with a second group of gas holes, the downstream slope of each undulation being provided with a third group of gas holes, a gutter member connected to the under side of the upstream slope of each hill and extending therefrom in the upstream direction to a position beneath the adjacent valley and downstream slope, the gutter member having an intermediate portion below the level of said adjacent valley and rising to a terminal portion higher than said intermediate portion and spaced from the downstream slope, the gutter member serving as a baffle to prevent gas from rising directly into said second and third groups of holes and causing it to take a circuitous path and also iaictling as a trough to receive liquid dripping from the 2. A tray for gas-liquid contact, of the type having an elongated liquid retention plate across which liquid is 1 made to flow in contact with the gas and a number of gas holes through the plate through which the gas is adapted to flow into and through the liquid stream, such plate having a series of hills and intervening valleys in the path of the liquid flow, a first group of gas holes being provided through the plate at the summit of the hills, a second group being provided through the plate at the valleys, and a third group being provided in the slope of the hills, the holes within the groups being evenly distributedso that any given perforated zone of the plate has an equal hole area, the resultant area of the holes being such that when gas is passing through all the holes-there is a resultant thrust of the gas against the liquid in the direction of flow of the liquid.

3. A tray for gas-liquid contact, of the type having an elongated liquid retention surface across which liquid is made to flow in contact with the gas, and a number of gas holes through said surface through which the gas is adapted to flow into the liquid stream, such surface being made up of a plurality of overlapping corrugated strips, each strip having an intermediate undulation flanked by a downstream valley portion and an upstream valley portion each ending in an upsweep portion, the strips being arranged in overlapping relationship with the downstream upsweep portion of one strip resting on the upstream side of the undulation on the next strip and with the upstream valley and upsweep portion of one strip underlying the downstream side of the undulation and the downstream valley of the preceding strip, each strip being provided with a plurality of groups of gas holes, a first group extending through the strip adjacent to the top of the undulation, a second group being located in the downstream valley portion, and a third group being located in the downstream face of the undulation.

4. A tray according to claim 3 in which the third group of gas holes is directed in the direction of flow of the liquid, and the resultant area of all the holes is such that when gas is passing through all the holes there is a resultant thrust of the gas against the liquid in its direction of flow.

5. A tray for gas-liquid contact, of the type having an elongated liquid retention surface across which liquid is made to flow in contact with the gas and a number of gas holes through the surface which the gas is adapted to flow into the liquid stream, such surface having a series of hills and intervening valleys running transversely to the path of the liquid flow, a first group of gas holes being provided through the plate at the hills, a second group being provided through the plate at the valleys, and a third group being provided in the slope of the hills, the third group of holes being directed in the direction of flow of the liquid, the resultant area of the holes being such that when gas is passing through all the holes there is a resultant thrust of the gas against the liquid in the direction of fiow of the liquid, the tray being of a circular shape and having a member adapted to engage the wall of a column, said member receiving the edges of said elongated liquid retention surface throughout a part of the circular periphery of the tray, downcomer means adapted to conduct liquid down to the next tray and onput means for receiving liquid from the preceding tray, the said liquid retention surface being made up in two halves and means associated with said liquid retention surface for supporting and securing together the respective halves.

6. In a column for contacting liquid with gas, a pair of spaced apart annular members engaging the inner wall of the column and forming therebetween a receiving channel, a perforated plate-like means adapted to provide a liquid supporting surface, said plate-like means being made up of a plurality of corrugated strips arranged in succession and in contacting relationship whereby a downstream portion of one strip engages an upstream portion of the succeeding strip, the ends of the strips being held in said channel whereby the strips are held in position to constitute said plate-like member.

7. A gas-liquid contacting tray comprising an annular liquid-receiving surface surrounding a central opening,

said tray having downcomer means adjacent said central opening, annular onput means at the periphery, 'and' 'ai member having a liquid-supporting surface between said onput means and downcomer means, said liquid-supporting surface having a plurality of undulations across which the liquid is adapted to run on its way from the onput means to the downcomer means, a first group of open ings at the top of the undulations, a second group of openings in the valley between the undulations, and .a third group of openings in the downstream slope of the undulations, the holes within the groups being evenly distributed so that any given perforated zone of the plate has an equal hole area, the resultant area of the openings being in the downstream direction whereby to exert a gas thrust on the liquid.

8. A gas-liquid contacting tray comprising an annular liquid-receiving surface surrounding a central opening, said tray having downcomer means adjacent said central opening, annular onput means at the periphery, and 'a member having a liquid supporting surface between said onput means and downcomer means, said liquid support ing surface having a plurality of undulations across which the liquid. is adapted to run on its way from thejonput means to thedowncomer means, a first group of openings near the top of the undulations, a second group of open: ings in the valley between the undulations, and a third group of openings in the downstream slope of the undulations, in which said liquid supporting surface is made up of a plurality of overlapping annular corrugated rings each having an undulation flanked by a downstream valley and an upstream valley ending respectively in upsweep portions, the downstream upsweep portion of each ring being fastened upon the upstream wall of the undulation of the succeeding ring, the upstream valley and adjacent upsweep portion of each ring underlying a downstream valley and adjacent upsweep portion of the preceding ring.

9. A gas-liquid contacting tray comprising an annular liquidreceiving surface surrounding a central opening, said tray having downcomer means adjacent said central opening, annular onput means at the periphery, and a member having a liquid supporting surface between said onput means and downcomer means, said liquid supporting surface having a plurality of undulations across which the liquid is adapted to run on its Way from the onput means to the downcomer means, a first group of openings near the top of the undulations, a second group of openings in the valley between the undulations, and a third group of openings in the downstream slope of the undulations, and in which the central opening contains a liquid-receiving bowl connected to the downcomer, a pipe enters the side of said bowl and projects therefrom in the direction towards the periphery of the tray upwards and then downwards, said pipe allowing flow of the liquid toward the periphery on the way to the next lower tray when the liquid reaches a certain level, said pipe having an opening in its uppermost portion to equalize pressure.

10. An element for use in trays of the type described for use in gas-liquid contacting trays, comprising, an elongated strip corrugated in its direction of length to have an intermediate hill flanked at each side by a valley and upsweep portion, one of said valleys being on the downstream side of the strip and the other valley being on the upstream side, the summit of the hill being provided with a first group of gas holes, the downstream valley being provided with a second group of gas holes and the downstream face of the hill being provided with a third group of gas holes, the strip being adapted to be associated with identical strips thereby to make up a liquid supporting plate with the downstream upsweep portion of one strip fastened upon the upstream slope of the hill of the subsequent strip.

11. A gas-liquid contacting tray comprising an annular liquid-receiving surface surrounding a central opening, said tray having downcomer means adjacent said aeagase Illl central opening, annular onput means at the periphery, and a member having a liquid-supporting surface between said onput means and downcomer means, said liquid supporting surface having a plurality of undulations provided with gas holes, across which the liquid is adapted to run on its way from the onput means to the downcomer means, and in which the central opening contains a liquid-receiving bowl connected to the downcomer, a pipe enters the side of said bowl and projects therefrom in the direction towards the periphery of the tray upwards and then downwards, said pipe allowing flow of the liquid toward the periphery on the way to the next lower tray when the liquid reaches a certain level, said pipe having an opening in its uppermost portion to equalize pressure.

' 12. A column for contacting liquid with gas having a plurality of trays one above the other over which the liquid is adapted to run in succession while the gas passes up through the trays of the liquid thereon in succession, each tray having a liquid-supporting surface, downcomer means at one side and onput means at the other side, each tray including an elongated plate having a series of hills and intervening valleys in the path of the liquid flow, a first group of gas holes being provided through the plate at the summit of the hills, a second group being provided through the plate at the valleys, and a third group being provided in the slope of the hills, the holes Within the groups being evenly distributed so that any given perforated zone of the plate has an equal hole area, the resultant area of the holes being such that when gas is passing through all the holes there is a resultant thrust of the gas against the liquid in the direction of flow of the liquid.

References Cited in the file of this patent UNITED STATES PATENTS France Ian. 13, 1954 OTHER REFERENCES Ser. No. 369,478, Stock (A.P.C.), published May 25, 1943, 

